How to develop software for a custom board without a 32kHz Xtal.

[gocchan]

Hello,
I'm prototyping a custom board equipped with a WBA23KE and developing its software.
Since this custom board doesn't have a 32kHz crystal, I modified the code based on BLE_p2pServer, referencing the description on the following website.
LSEクリスタルなしでSTM32WBA上でRFアプリケーションを動かす方法 - stm32mcu
However, the HAL_RTC_Init() function on line 615 of the attached main.c fails and goes into ErrorHandler().
How should I modify the code?

[Pavel A.]

In line 323 HAL_PWR_EnableBkUpAccess() is commented out. Uncomment  it.

 

[gocchan]

I commented it out, but the situation didn't change.